Intracapsular and para-articular osteochondromas are a rare subtype of soft tissue chondroma occurring in and around joints. We report a giant 5.5cm × 5.5cm × 3.0cm mass occurring in the knee of a 45 years old lady and examine previous cases to update our understanding of para-articular soft tissue osteochondromas.

Clinicopathological data were obtained from medical records for the case report whilst a multi-database literature search was conduction for the literature review. 27 articles containing 39 cases were identified in the English literature under our strict inclusion criteria. Along with our data, 40 cases were collated and analysed to provide a set of reference characteristics. These included: age, male-female ratio, spatial location, time of onset, tumour size, clinical symptoms, mechanism of injury, investigations used, treatment received, histopathology features, follow-up and recurrence characteristics. Statistical analysis was performed on data to elicit any discernable pattern of tumour formation.

Median age of patients was 50 years old with a male to female ratio of 1:1.11. Most commonly occurs in the 40s, 50s and 60s accounting for two-thirds of all cases. Majority of tumours were located within or adjacent to a fat pad structure. 33 were located in the infra-patellar region, 3 in the suprapatella/pre-femoral region and 4 in other para-articular locations. Average time of onset to diagnosis was 5.81 yrs with a mean volume of 87.5 cubic centimetres. No discernable correlation between time of onset to diagnosis and tumour size was found (spearman correlation co-efficient 0.534, p=0.007). The main symptom reported was pain in 29 cases, whilst 5 were pain free, 6 cases were unspecified. X-Rays, CT and MRI have become the core imaging modalities in investigation. En bloc excision is the choice of treatment, whilst arthroscopic techniques have also been used with similar success. Histologically, 35 cases had a typical description of a cartilage capped lesion with central trabecular bone and areas of endochondral ossification. 3 cases had a histological appearance of predominantly bone whilst 2 cases had predominantly cartilage. All tumours analysed were benign. No recurrences were reported with an average follow up period of 1.91 years.

We have provided the latest set of data for the characterisation of para-articular and intracapsular soft tissue osteochondromas. These tumours are benign entity with an invariably good outcome following simple excision. Recognition of this entity is important to prevent over investigation and the performance unnecessarily invasive and radical procedures.